Background: Nearly 90% of out-of-hospital cardiac arrest (OHCA) patients are witnessed, yet only 2.3% received bystander CPR (cardiopulmonary resuscitation in Pakistan. This study aimed to determine retention of knowledge and skills of Hands-Only CPR among community participants in early recognition of OHCA and initiation of CPR in Karachi, Pakistan.Methods: The pre and post-tests were conducted among participants from diverse non-health-related backgrounds from July 2018 to October 2019. Participants were tested for knowledge and skills of CPR before training (pre-test), immediately after training (post-test), and six months after training (retention test). All the participants received CPR training through video and scenario-based demonstration using manikins. Post-training CPR skills of the participants were assessed using a pre-defined performance checklist. The evaluator read out numerous case scenarios to the participants, such as drowning, poisoning, and road traffic injuries, etc., and then asked them to perform the critical steps of CPR identified in the scenario on manikins. The primary outcome was the mean difference in the knowledge score and skills of the participants related to the recognition of OHCA and initiation of CPR. Results: The pre and post-tests were completed by 722 participants, whereas the retention test after 6 months was completed by 358 participants. The mean knowledge score related to the recognition of OHCA, and initiation of CPR improved significantly (p <0.001) from pre-test (47.2/100, ±13.2) to post-test (69.9/100, ±12). The mean CPR knowledge after six months (retention) reduced slightly from (69.9/100, ±12) to (64.8/100, ±9.3). The CPR skill retention for various components (correct placement of the heel of hands, complete chest recoil, check for scene safety, check for a response, and activate emergency response system) slightly deteriorated from 79% in the post-test to 72% in re-test. However, participants performed slightly better on achieving an adequate rate of chest compressions from 73.7% in post-test to 75.5% in re-test.Conclusion: Community members with non-health backgrounds can learn and retain CPR skills, allowing them to be effective bystander CPR providers in OHCA situations. We recommend training the mass population in Pakistan regarding CPR to increase the survival rate from OHCA.